A Good Man Goes to War
by Just Iowa
Summary: Humanity's grief-stricken champion falls victim to a Slipspace accident, throwing him into the Doctor's TARDIS. John faces an enemy that is eerily similar to him. Will he find his humanity among machinery?
1. Chapter 1: Accidents Happen

**UNSC INFINITY, 2557**

John-117 held his new helmet in his iridescent green gauntlets. He turned it over and looked at his reflection in the golden visor, feeling the memories of receiving the earlier models come rushing back. MJOLNIR Mark IV had changed him. He found a part of his identity in the suit. It made him stronger, faster, and more effective almost as if it was a dream come true for him. Sometimes, though, the few times he went without the armor he felt as empty as the suit was without him.

Mark V had marked the beginning of the end for his squadmates-his friends, he corrected himself-but had made it possible for him to survive the Halo event and carry Cortana. Curiously, his new Mark VII helmet closely resembled the earlier Mark V, which started a wave of nostalgia for the days with Cortana when he was the knight in shining armor._ Funny connection. Not many knights can claim to have a shield made of energy. Maybe I'm just getting sentimental_, John thought. _Maybe I am getting old. Maybe I am breaking without her_.

Cortana and John had formed a nearly unbreakable bond through a nearly symbiotic connection. Combined with the fact that they saved all life in the galaxy a handful of times, it wasn't a surprise they shared such a strong connection. Cortana had picked him as though it was for a Sadie Hawkins dance, although the survival of humanity was on the line and the thought of asking someone to a dance has a tendency to be a scarier thought than genocide for most. She picked him not because he was the best at anything statistically-which would be right up her alley seeing as she is a smart AI-but her inner bad girl chose him because he was the luckiest._ Now she's gone. Remembering how it was isn't helpful. I need to move on_. He blamed himself for her death. He sacrificed his queen to defeat the Didact. Sometimes he wished he had sacrificed the king instead. They had been apart before when he was forced to leave her behind on the High Charity. The Gravemind made her a puppet and used her to shake the rock-hard resolve of a SPARTAN-II. He vowed to himself after that day to protect her no matter the cost. In the end, she was afflicted by rampancy while he desperately tried anything to extend her lifetime. He knew he couldn't save her yet he refused to admit it. He stubbornly insisted on holding on to her even when she was already gone. The aging Spartan shook his head to clear his thoughts.

He clutched Cortana's dead chip in his newly armored hand and glanced at it before he put his new helmet back on. The eggheads had left him to test out his new gear in peace and discover its features himself; Lasky's orders, probably. So far, he noted that the shields were a good portion stronger than his Mark VI, approximately 30% higher damage threshold before failing. During live-fire training, he noticed a heavier focus on recoil-reduction and targeting systems. The visor received a cut-down version of the scanning systems he had picked up on Requiem and could paint targets through obstructions up to 20 meters away. He practiced diligently in the Combat Deck, the hologram room that could replicate any location known to man. This is where simulations took place. Often, he fought once more on Installation 04. The holograms he chose to engage were those of himself. Nobody on Infinity but John himself could give you a reason why. The team of scientists in charge of briefing him and orienting him before they turned him loose happened to mention that the suit contained a full Slipspace drive, not just de-insertion units that the earlier versions of Mark VII had. He was more interested in the fact that the suit utilized nanotechnology to repair itself and upgrade itself to adapt to combat conditions. However, he was curious about its capabilities now that he had tested the rest of the suit extensively. He decided to carry a sturdy MA5D with him and holster a standard-issue M6H as a precaution in case he ended up being dragged into another battle for the survival of all life in the galaxy as he had a habit of doing. He set a course to the control room of Infinity; he was only going to do a short run to test out the accuracy of the unit. John fired up the drive and prepared for a rough ride.


	2. Chapter 2: The Two Couples

ANAMOLOUS SLIPSPACE DIMENSION ACCORDING TO UNSC LOGS, DATE UNKNOWN

The Master Chief opened his eyes to an unfamiliar sight. Due to a lifetime of training, he immediately assessed the situation. It was definitely a control room but it wasn't the correct control room. No immediate environmental hazards. His augmented eyes swept the room with incredible speed, taking note of every minor detail as if he was a great detective carrying the surname of Holmes. His gaze snapped to an oddly dressed man with a rather oddly shaped chin and he drew his MA5D faster than it seemed humanly possible, steadying it and readying it to fire. The strange man threw up his hands in a gesture of peace, but the Spartan was not fazed. "Identify yourself!" the Chief roared. "I'm the Doctor!" the man responded. "I'm unarmed, see?" as he waved his hands in the air and exposed the inside of his jacket. John remained wary and waited for further explanation. "Although I should be asking you that because I want to know how you got on my ship and I should be informed as to who this visitor happens to be!" the Doctor retorted. "This is UNSC Master Chief Petty Officer Spartan-117 and you should know that if you make one wrong move you will be neutralized immediately." He lowered his assault rifle. "Is that clear?" The Doctor nodded quickly. "Now what is this ship and where are we headed?" Now that the crisis was averted, the Doctor began a speech that he had become accustomed to giving. "We are on the TARDIS; it stands for Time And Relative Dimension In Space. It's bigger on the inside-go on, have a peek outside-and is currently flying gracefully like a brick-no, that's not right, bricks don't fly-through the time vortex. Now, I'll answer more questions once you provide me with the answer to how you boarded my ship." John holstered his rifle in the magnetic strip on the back of his armor as it was clear this man was not a threat and he would have to work with him to get out of this situation. "By means of personal Slipspace drive. It appears to have been a miscalculation." John answered. "Miscalculation? These things don't happen by coincidence. Oh, I remember the Slipspace drives right before the vortex manipulators...too early? Evidently so. Anyway, there is a reason our time streams collided and I'll be optimistic and assume that this is the universe's way of finding the right tool for the job." The Chief listened carefully. "This ship can travel through all four basic dimensions, correct? If I agree to assist you in your objectives, I would need compensation." "And this would be...?" "Returning to save her." John held up Cortana's lifeless chip. The Doctor immediately recognized the structure of the chip as nearly identical to a data core of his TARDIS. He knew that this one was different, however. It housed a smart AI: a digital construct that had a personality and learned similarly to humans yet retained all the advantages of being a computer. Smart AIs were rarely made because of high production cost-some were even made from cloned human brains-and that they were afflicted by a condition known as rampancy after a service life of 7 years. Rampant AI experienced delusions of godlike powers and began to fragment, eventually arguing with multiple versions with themselves and ripping themselves apart. They literally thought themselves to death. He concluded that was the fate of the AI that had once abided in that chip. He didn't believe it was possible to revive an AI destroyed by rampancy. I would need to rewrite everything to revive her, which would be impossible. Going line by line slaving away to fix the bugs...hold on. "Copy and paste!" the Doctor blurted out. The Chief cocked his head and said, "So you're telling me there is a way?" It's a long shot, but I can travel to the point of assembly and copy the original source. "There's a chance," said the Doctor. "That maybe we could simply make a copy of the unmodified AI, a very simple and common occurrence for most AIs. Obviously if that's all you want in return for a task that you don't have a clue about yet then it-she-must be very valuable to you. Does she have a name?" The Master Chief shifted uncomfortably. He never was one for conversation. "Cortana." he answered after a tangible pause. The Doctor stopped fiddling with the settings on his sonic screwdriver long enough to direct full attention to John and say, "Yes. I know that one." before reverting his attention to the control board and hitting a few big friendly buttons. "How...?" was the only response John had. He had begun to pace around the control room, inspecting the Doctor's ship, who clearly had a few screws loose. The Doctor never answered him. To confirm the Doctor's statement that it was, in fact, bigger on the inside, John swung open the doors and peered out to examine the exterior of the ship. It certainly was. He noted that this was not the first time he had seen this technology. He had personal experience with the Forerunner's experiments with dimensional fields, and while on the Infinity he had even heard of the Dyson Sphere and the various pocket dimensions the Forerunners used in their Shield Worlds. "Shocked?" the Doctor queried. John shook his helmet to respond in the negative. "That's a first." the strange man replied, almost as if he was genuinely surprised at John's lack of amazement and disbelief. "Give me your chip." he ordered. John is not typically one to question authority, but he was going to guard what remained of his companion, teammate, and friend from any threat and he still was rather wary of this strange man. Yet, he held out the chip to the Doctor because he was confident he could crush him in his bare hands if he had to. "Your AI friend has an identical structure to my TARDIS, so if we pass through the timeline the two will interface..." he slotted the chip into a perfectly sized port. "...And her entire source code will redownload, the memories will reinstall, and it should be done right about...now!" The chip popped out with a ding like toast out of a toaster on a Sunday morning; only this toast was of much greater importance to the galaxy. John held it out in front of him tenderly after retrieving it. A lively blue glow began to run in tiny creeks over the surface of the cold metal. An orb began to form, pulsing and contorting into various shapes like a misshapen water balloon. Finally, it flared and returned to a familiar form. Cortana looked up and brushed her now-long hair out of her glowing eyes, saying a silent hello to the silent hero.


	3. Prologue

_Demons Run when a Good Man goes to war._

_Night will fall and drown the Sun  
_  
_When a Good Man goes to war.  
_  
_Friendship dies, and true love lies;  
_  
_Night will fall, and the dark will rise  
_  
_When a Good Man goes to war._


	4. Chapter 3: Men of Steel

**LOCATION: UNKNOWN, NEAR UNSC DESIGNATE 'REQUIEM' DATE: ?/?/2557**

The travelers arrived at their destination: the derelict UNSC Forward Unto Dawn. John threw open the doors of the TARDIS, surveying the abandoned ship that had carried him to Requiem a few months prior. "Why did we come here?" the Chief asked. The Doctor simply gestured with a sweeping motion towards the blur that was beginning to materialize near the ship. "Cortana, what is that?" the Spartan inquired.

"When I was being downloaded to the TARDIS data core, I took some opportunities to copy some important information from her. _She_ was rather jealous of me. That is a Cyberman mothership entering from a tear in the barriers between parallel universes. This is frequently caused by multiple major events in history having an equal chance of occurring-sometimes it causes both possibilities to occur at once-crossing one's own time stream is significant as well. The Cybermen are armed and possess weapons that may prove effective against your shields. I would recommend to avoid combat unless absolutely necessary." Cortana said from the hologram held in John's gauntlet.

The Doctor interrupted. "No. No combat. Nobody dies. Not in my name."

The Master Chief retorted, "Very few men will dare to provoke us. Intimidation is a useful tactic in negotiations."

"These are not quite men that we face." the Doctor mumbled.

Clearing his throat, he began to brief the Chief. "The Cybermen are sending a salvage team to take your suit and reverse-engineer it in order to upgrade themselves. They plan on taking your body and putting you in their modified suit because they deem you already compatible without any emotional inhibitors. We cannot allow this to happen at any cost. Fixed points in your future would be overwritten and the two parallel universes would merge. Of course, it certainly wouldn't be healthy for the rest of the universe if the Cybermen got their tin-can hands on energy shielding technology. They might even be able to defeat Daleks if that happened."

John listened patiently. "How are we going to stop them?" he asked.

"I don't know yet!" the Doctor exclaimed almost gleefully.

Spartan-117 slid Cortana into his neural port and said simply, "Cortana can take care of that."

Cortana interjected. "According to the TARDIS databases, crossing our own time stream would be catastrophic. They are after the version of you in cryosleep, but this version would suffice as well so we need to watch our step. Or, if they find this version of me, they would have access to data about the Prometheans below and possibly try to convert themselves into them instead. That would still be equally as bad and our timeline would still be overwritten. The best plan I can generate so far is to use me to infiltrate their navigation system and reroute them back to their universe before overloading their engines. I can set this on a delay so we have time to escape."


End file.
